The present invention relates to a charge-coupled device (CCD), and more particularly, to a CCD and method of manufacturing the same which prevents smear and improves sensitivity.
FIGS. 1A and 1B are sectional views of a conventional CCD. Referring to FIG. 1A, in the conventional CCD first and second p.sup.- type wells 11 and 12 are formed on an n type substrate 10. An n.sup.+ type photodiode 14 and n.sup.+ type vertical charge coupled device (VCCD) 15, which is the charge transmission domain, are formed on first and second p.sup.- type wells 11 and 12. A p.sup.++ type surface isolation layer 16 is formed on n.sup.+ type photodiode 14. A third p.sup.- type well 13 is formed to surround n.sup.+ type VCCD 15. A p.sup.+ type channel stop 17 is formed to insulate pixels therebetween.
A gate insulator 18 is formed on the overall surface of the substrate. A transmission gate 19, interlevel insulator 20 and light-shielding layer 21 are formed sequentially on gate insulator 18 above VCCD 15. A passivation layer 22 is formed on the overall surface of the substrate.
A first planarization layer 23 is formed on passivation layer 22. A color filter layer 24 is formed on first planarization layer 23 above photodiode 14. A second planarization layer 25 is formed on first planarization layer 23 including color filter layer 24. A microlens 26 is formed on second planarization layer 25 above color filter layer 24.
In the conventional CCD, light coming through a camera lens is converged by microlens 26 and passes through color filter layer 24. Light selectively passing through color filter layer 24 is incident upon photodiode 14, and photoelectrically converted into charges. These charges produced from the photodiode through photoelectric conversion are transmitted to VCCD 15 and then vertically to a horizontal charge coupled device (HCCD) by a clock signal of VCCD 15. The charges transmitted to the HCCD (not shown) are horizontally transmitted by a clock signal of the HCCD. The horizontally transmitted charges are detected as a voltage due to the device ends' floating diffusion. The voltage is amplified to be transmitted to the peripheral circuits.
As shown in FIG. 1B, in the conventional CCD, light incident upon the center of the microlens comes into photodiode 14 to be photoelectrically converted into signal charges. However, light incident on the periphery of the microlens enters VCCD 15 and is photoelectrically converted into smear charges. These smear charges cause the smear phenomenon. In case of long-wavelength light, the light incident on microlens 26 passes through the photodiode and enters first p.sup.- type well 11, producing undesirable signal charges. In addition, the step height in the photodiode and VCCD becomes high.